Off-Axis Guider vs Guide Scope

Hi,

I'm starting to get into astrophotography. I've been doing a lot of reading on the web about whether Off-Axis Guider or Guide Scope are better for guiding, be it automatic or manual.

From reading many of the posts here, it seems Guide scope are the way to go, but then you have to deal with Differential Flexure, (and probably more that I know no idea about) What I havent seen to much of or about is anybody using Off-Axis guiders. Anyone have any experiences on which is best, pros/cons etc...

Sorry if this topic was already covered.

Cheers,
Gary.

Gary,

The problem with an off axis guider is locating a suitable guidestar on the ccd of your auto-guiding camera. I have given this a go and really it is very difficult to find a suitable star.

The flexure problem with a guide scope is not nearly so serious and is much easier to deal with. Saying that do make sure you get a really solid set of guide scope rings. I use losmandy rings and they are first class. You can get others too but this is one area where you do get what you pay for.

My best advice is get a short focal length guidescope, and a really solid set of rings. With a guidescope of 600mm focal length or shorter you will almost certainly find a guidestar anywhere you point the scope.

Just noticed you have a nexstar 8SE. Do you have an equatorial wedge for it? If not, no amount of autoguiding will give you round stars due to field rotation which is unavoidable in alt/az mode. You can get away with short exposures but then you dont even need an autoguider to do that.

Hi Dave,

Thanks for the info, I was wondering why more dont use them. Im just about to get a CG-5 goto, and will be using the 8" OTA with it. (was thinking about the wedge, and after doing a lot of research wouldn't bother with it).

Cheers for the info. I start looking down the Guide Scope road so!

Cheers,
Gary.

Im just about to get a CG-5 goto, and will be using the 8" OTA with it. (was thinking about the wedge, and after doing a lot of research wouldn't bother with it).

Gary,

I whole-heartedly agree that the CG5 will be a much better option. Wedges are too prone to vibration by even the slightest breeze and are a right pain to polar align.

yea, I'd agree there, a wedge is really for a permanent observatory setup, I tried using it in the field and it makes life real hard.